Woah, duck out for two days and I end up 200 posts behind! This thread is craaaaazy...
Anyway, 'twas indeed good fun on Saturday and I enjoyed the hifi, the music, and the company (and the mind-altering substances) very much. AK's system is very cool. Bub and I tried hard but there really wasn't much to criticise about it at all.
Bub's theory about the crossover messing up the midrange (and thus the monitors sounding better without the bass boxes) is controversial at best - I
think I
may have heard a difference in the mids, but the extra solidity and body that the bass bins contributed seemed like a much more noticeable (and desirable) effect.
I will say that the tonal balance isn't
quite to my preference - but that's true of 99.9% of non-ATC-based systems I've heard.

It's just that nobody does midrange like ATC... So, yeah I suppose the midrange was a tad recessed for my tastes. But it wasn't a big deal. I just happen to be very picky.
The only other thing that I wasn't 100% convinced by was the whole "open, airy" soundstage. I've not yet made up my mind whether this effect is real, or if it's just a trick of the audiophile speaker designer's trade. (Maybe something in the crossover? Or the tweeters?) I do know that ATCs, and a few other very high quality systems I've heard, don't do "open and airy" except on particular discs - usually live recordings (or 'live in studio'), often older ones. Most modern multitracked recordings don't have much in the way of airiness at all on ATCs - there isn't any acoustic to hear, just the specific instruments/voices/sounds poisitioned in between the speakers according to the sound engineer's whim. But throw on something like my recently-discovered and much-loved Duke Ellington compilation CD of live recordings from the 50s and early 60s and all of a sudden you can
hear the room. It's quite uncanny, and very cool.
It seems to me that audiophiles/phools are just conditioned to expect this "artificial" airiness that so many hifi systems produce. I have to admit it can be quite seductive. But it just doesn't seem
real to me - and I've come to the conclusion that
reality is my biggest turn-on in hifi. I want to be able to close my eyes and
believe that the singer or instrument or orchestra is there in front of me (or, even better, that I'm
in the room with them). My ATCs (and Bub's, and a few other systems I've heard that I could count on one hand) do this to a degree that pleases me.
I will also concede that it's possible the "airiness" effect is in fact a result of higher quality speaker design (better tweeters, crossovers, baffles, whatever) and the ATCs are in fact missing something. But I'm not yet convinced.
Anyway, sorry, my ranting wasn't actually directed specifically at AK's system. Indeed, his ARTs (especially when toed-in towards the listener) are quite subtle in their use of "air", enough that I wasn't bothered by the effect much at all - though AK likes them better with less toe-in and thus more air.
So, yeah, great system.

Superb rhythm, pacing, etc, very quick, very clean, very smooth, ass-kicking dynamics and bass (that power amp is really something), frightening loudness capability, and really just a lot of fun. But I still like mine better.
Many thanks for being such a generous host, Paul, and look forward to doing it again some time.
Dunc